In order to achieve safe driving of a vehicle, research and development on a device which automatically controls steering, accelerator and brake of a vehicle to detect a dangerous event around the vehicle and to avoid the detected dangerous event are being conducted, and such a device has been already mounted on some vehicles. Among them, a system that detects an obstacle such as vehicles or pedestrians in front of a vehicle with a camera mounted on the vehicle and gives warning to the driver or an automatic brake is effective in view of improving safety of the vehicle.
In a system which detects obstacles around an automobile from an image of a camera mounted on the automobile, it is particularly important to detect a pedestrian having a possibility of collision with the automobile in terms of the pedestrian protection. In particular, in order to improve safety, it is important to detect pedestrians jumping out of the shadow at an early stage and to perform braking control for preventing collision with pedestrians. Collision prevention performance against pedestrians jumping out of the shadow is also planned to be incorporated into a safety performance determination reference for European Euro-NCAP. Examples of a detecting sensor include a millimeter wave radar, a laser radar and a camera, but a method of using a camera, particularly a stereo camera, is described in PTL 1.
The contents described in PTL 1 disclose the invention in which a distance measuring unit based on monocular information and a distance measuring unit based on stereo information are used when an obstacle is detected by a stereo camera, a distance measuring unit based on the stereo information is used in the obstacle detection of a portion close to the vehicle, a distance measuring unit based on the monocular information is used in the obstacle detection in a portion remote from the vehicle, the two measuring units are switched by the detected distance, and particularly when there is a risk of a degradation of the accuracy, the distance which applies the distance measuring unit based on the stereo information is set to be longer.